Being salts of a hydroxyl-containing organic acid, γ-hydroxybutyric acid salts can partially dissolve in organic solvents. For this reason, γ-hydroxybutyric acid salts are used to hydrolyze organic halides, such as those having alkyl group, alkenyl group, allyl group and other organic functional groups, and serve as a useful reaction reagent to derive corresponding esters and alcohol derivatives.
γ-hydroxybutyric acid salts can be readily obtained by reacting γ-butyrolactone with a hydroxide or a carbonate of an alkali metal or an alkaline earth metal. Since this reaction is generally performed in the presence of water, γ-hydroxybutyric acid salts are obtained as aqueous solutions. To make such solutions usable in reactions such as hydrolysis or esterification, the solutions must be dehydrated to adjust water concentration. This, however, often results in the formation of crystallized γ-hydroxybutyric acid salts. For this reason, a proper aprotic solvent always needs to be selected and used in the reaction.
When an aqueous solution of a γ-hydroxybutyric acid salt is dehydrated, a 4,4′-oxybis(butyric acid) salt, which is an ether dicarboxylic acid formed as a result of the dehydration and subsequent dimerization, is generated as a byproduct (4,4′-oxybis(butyric acid) and its metal salts may be referred to as EDCA and EDCAM, hereinafter). For example, German Patent No. 919167 describes that EDCA is generated at 50 to 55% yields by mixing γ-butyrolactone with a hydroxide of an alkali metal or an alkaline earth metal at 120 to 130° C., then heating the mixture at 180 to 230° C. in the presence of aluminum oxide, and then dehydrating the mixture for 8 to 10 hours. The German patent also describes that EDCA is generated at similar yields even in the absence of aluminum oxide whereas the dehydration takes twice as long. Thus, despite their usefulness as a reagent to promote hydrolysis and other reactions, the preparation of concentrated aqueous solutions of γ-hydroxybutyric acid salts is inevitably accompanied by the generation of EDCAM byproducts.
On the other hand, Japanese Patent Examined Publication Nos. Sho 64-9299 and Sho 64-9300 each disclose a production method for 2,2,2-trifluoromethanol, in which a γ-hydroxybutyric acid salt is reacted with 1,1,1-trifluoro-2-chloroethane in the presence of γ-butyrolactone that serves as an aprotic polar solvent. What is notable about this process is that the γ-butyrolactone, aside from reacting with the alkali metal hydroxide or carbonate to form a γ-hydroxybutyric acid salt as a raw material, serves as a solvent. Not only is the resulting γ-hydroxybutyric acid salt used to directly generate the desired 2,2,2-trifluoroethanol, but it is also converted to γ-butyrolactone after the reaction and can thus be recycled. For these reasons, the process is highly advantageous.
To date, production of 2,2,2-trifluoroethanol has required the γ-hydroxybutyric acid salts produced by the above-described process. The resultant 2,2,2-trifluoroethanol is separated from the reaction mixture by distillation, and the solution remaining in a still after distillation is recycled as an aprotic polar solvent containing γ-butyrolactone. The recycle process involves separating the salt byproduct from the still residue. This separation step has posed many problems. Specifically, the residual solution often becomes excessively viscous and organic materials and solvents may stick to the salt byproduct, making it difficult to separate the salt byproduct by filtration. As a result, a significant solvent loss may occur and the crystallized salt byproduct may form large clumps together with organic materials. In addition, the salt byproducts so produced are often unsuitable for use as fertilizers and may result in increased amounts of waste material. Each of these problems is critical to an industrial process and must be eliminated.